The Suitability of 3-D Printed Eutectic Gallium-Indium Alloy as a Heating Element for Thermally Active Hydrogels

We report the use of a novel extrusion tip that allows for the omnidirectional printing of eutectic gallium-indium (eGaIn) alloy onto the surface of hydrogel materials into complex 2-dimensional patterns. The use of these printed soft "wires" as an electrothermal heating element for soft robotics purposes was explored. Heating of the eGaIn structures encapsulated in an alginate/acrylamide ionic-covalent entanglement hydrogel was measured by a thermal imaging camera. It was determined that eGaIn is a suitable material for use in future soft robotics applications as an electrothermal heating element to actuate thermally responsive N-isoproylacrylamide hydrogels.